El déficit de lipasa ácida lisosomal como paradigma de enfermedad de depósito multisistémica / Lysosomal acid lipase deficiency as a paradigm of multisystemic storage disease

Las enfermedades de depósito lisosomal son un grupo de enfermedades que ha cambiado su pronóstico y manejo clínico en los últimos 15 años gracias a la aparición de tratamientos enzimáticos sustitutivos. La mayoría de las formas clínicas diagnosticadas eran síndromes clásicos graves; el avance de los métodos diagnósticos de función enzimática hace que se hayan diagnosticado e identificado formas más leves que han pasado desapercibidas, pero que a pesar de ello asocian una elevada morbimortalidad, y en las cuales el tratamiento es incluso más efectivo que en las formas graves. El déficit de lipasa ácida lisosomal es una de estas enfermedades lisosomales por depósito de ésteres de colesterol y triglicéridos que cumplen con todas estas características. El tratamiento enzimático sustitutivo con la enzima recombinante sebelipasa ha cambiado el pronóstico infausto de las formas graves. Los métodos diagnósticos de análisis enzimático en gota seca están identificando formas más leves en la infancia tardía y la vida adulta en pacientes con hipercolesterolemia y afectación hepática que estaban sin diagnóstico o mal diagnosticados.(AU)

Lysosomal storage diseases are a group of diseases whose prognosis and clinical management have changed in the last 15 years thanks to the appearance of enzyme replacement treatments. Most of the diagnosed clinical forms were severe classic syndromes; the advance of diagnostic methods of enzymatic function has meant that milder forms that had previously gone unnoticed have been diagnosed and identified. However, in spite of this they are associated with high morbidity and mortality, and in which treatment is even more effective than in severe forms. The lysosomal acid lipase deficit is one of these lysosomal diseases due to the deposition of cholesterol esters and triglycerides that fulfill all these characteristics. Enzyme replacement treatment with the recombinant enzyme sebelipase has changed the poor prognosis of the severe forms. Diagnostic methods of dry smear enzyme analysis are identifying milder forms in late childhood and adult life in patients with hypercholesterolemia and liver involvement who were undiagnosed or misdiagnosed.(AU)

Addressing neurodegeneration in lysosomal storage disorders: Advances in Niemann Pick diseases.

Most lysosomal storage disorders (LSDs) cause progressive neurodegeneration leading to early death. While the genetic defects that cause these disorders impact all cells of the body, neurons are particularly affected. This vulnerability may be explained by neuronal cells' critical dependence on the lysosomal degradative capacity, as they cannot use division to eliminate their waste. However, mounting evidence supports the extension of storage beyond lysosomes to other cellular compartments (mitochondria, plasma membrane and synapses) as a key event in pathogenesis. Impaired energy supply, oxidative stress, calcium imbalance, synaptic failure and glial alterations may all contribute to neuronal death and thus could be suitable therapeutic targets for these disorders. Here we review the pathological mechanisms underlying neurodegeneration in Niemann Pick diseases and therapeutic strategies developed in animal models and patients suffering from these devastating disorders. This article is part of the special issue entitled 'The Quest for Disease-Modifying Therapies for Neurodegenerative Disorders'.

The lysosomal storage disorders mucolipidosis type II, type III alpha/beta, and type III gamma: Update on GNPTAB and GNPTG mutations.

Mutations in the GNPTAB and GNPTG genes cause mucolipidosis (ML) type II, type III alpha/beta, and type III gamma, which are autosomal recessively inherited lysosomal storage disorders. GNPTAB and GNPTG encode the α/ß-precursor and the γ-subunit of N-acetylglucosamine (GlcNAc)-1-phosphotransferase, respectively, the key enzyme for the generation of mannose 6-phosphate targeting signals on lysosomal enzymes. Defective GlcNAc-1-phosphotransferase results in missorting of lysosomal enzymes and accumulation of non-degradable macromolecules in lysosomes, strongly impairing cellular function. MLII-affected patients have coarse facial features, cessation of statural growth and neuromotor development, severe skeletal abnormalities, organomegaly, and cardiorespiratory insufficiency leading to death in early childhood. MLIII alpha/beta and MLIII gamma are attenuated forms of the disease. Since the identification of the GNPTAB and GNPTG genes, 564 individuals affected by MLII or MLIII have been described in the literature. In this report, we provide an overview on 258 and 50 mutations in GNPTAB and GNPTG, respectively, including 58 novel GNPTAB and seven novel GNPTG variants. Comprehensive functional studies of GNPTAB missense mutations did not only gain insights into the composition and function of the GlcNAc-1-phosphotransferase, but also helped to define genotype-phenotype correlations to predict the clinical outcome in patients.

Aspectos actuales de la enfermedad de Fabry / Current aspects of Fabry's disease

No disponible

Loss of CLN7 results in depletion of soluble lysosomal proteins and impaired mTOR reactivation.

Defects in the MFSD8 gene encoding the lysosomal membrane protein CLN7 lead to CLN7 disease, a neurodegenerative lysosomal storage disorder belonging to the group of neuronal ceroid lipofuscinoses. Here, we have performed a SILAC-based quantitative analysis of the lysosomal proteome using Cln7-deficient mouse embryonic fibroblasts (MEFs) from a Cln7 knockout (ko) mouse model. From 3335 different proteins identified, we detected 56 soluble lysosomal proteins and 29 highly abundant lysosomal membrane proteins. Quantification revealed that the amounts of 12 different soluble lysosomal proteins were significantly reduced in Cln7 ko MEFs compared with wild-type controls. One of the most significantly depleted lysosomal proteins was Cln5 protein that underlies another distinct neuronal ceroid lipofuscinosis disorder. Expression analyses showed that the mRNA expression, biosynthesis, intracellular sorting and proteolytic processing of Cln5 were not affected, whereas the depletion of mature Cln5 protein was due to increased proteolytic degradation by cysteine proteases in Cln7 ko lysosomes. Considering the similar phenotypes of CLN5 and CLN7 patients, our data suggest that depletion of CLN5 may play an important part in the pathogenesis of CLN7 disease. In addition, we found a defect in the ability of Cln7 ko MEFs to adapt to starvation conditions as shown by impaired mammalian target of rapamycin complex 1 reactivation, reduced autolysosome tubulation and increased perinuclear accumulation of autolysosomes compared with controls. In summary, depletion of multiple soluble lysosomal proteins suggest a critical role of CLN7 for lysosomal function, which may contribute to the pathogenesis and progression of CLN7 disease.

The brain lipidome in neurodegenerative lysosomal storage disorders.

Cholesterol, sphingolipids and glycerophospholipids are critical constituents of the brain, subserving neuronal membrane architecture and providing a platform for biochemical processes essential for proper neurodevelopment and function. When lysosomal defects arise in a lipid metabolic pathway, it is therefore easy to imagine that neurological decline will transpire, however for deficits in non-lipid pathways, this becomes harder to envisage. Here we suggest the working hypothesis that neurodegenerative lysosomal storage disorders might manifest as primary and/or secondary disorders of lipid metabolism. Evidence suggests that the mere process of lysosomal substrate accumulation, ubiquitous in all lysosomal storage disorders, impairs lysosome integrity resulting in secondary lipid accumulation. Impaired lysosomal degradation of a specific lipid defines a primary disorder of lipid metabolism and as these lysosomal storage disorders additionally show secondary lipid alterations, all primary disorders can also be considered secondary disorders of lipid metabolism. The outcome is a generalized cellular lipid dyshomeostasis and consequently, the physiological architecture of the lipid-enriched plasma membrane is perturbed, including the lipid composition of specialized membrane microdomains, often termed lipid rafts. Neurotoxicity results from the complex interplay of malfunctioning signaling and vesicular trafficking important for neuronal communication and synaptic plasticity-induced by the imbalance in physiological membrane lipid composition - together with compensatory mechanisms aimed at restoring lipid homeostasis.

Two novel CPS1 mutations in a case of carbamoyl phosphate synthetase 1 deficiency causing hyperammonemia and leukodystrophy.

BACKGROUND: Carbamoyl phosphate synthetase 1 deficiency (CPS1D) is a rare autosomal recessive disorder of the urea cycle, mostly characterized by hyperammonemia and the concomitant leukodystrophy. The onset of CPS1D can be at any age, and the clinical manifestations are variable and atypical. Genetic tests are indispensable for accurate diagnosis of CPS1D on the basis of biochemical tests. METHODS: Blood tandem mass spectrometric analysis and urea organic acidemia screening were performed on a Chinese neonatal patient with low activity, recurrent seizures, and hyperammonemia. Next-generation sequencing and Sanger sequencing were followed up for making a definite diagnosis. Bioinformatics tools were used for the conservation analysis and pathogenicity predictions of the identified mutations. RESULTS: Increased lactate in urea and decreased citrulline in blood were detected in the patient. Two novel mutations (c.173G>T, p.G58V in exon 2 and c.796G>A, p.G266R in exon 8) in CPS1 identified in the neonatal patient were found through coseparation verification. Both of the two mutations were predicted to be deleterious, and the two relevant amino acids exerted highly evolutionarily conserved. The final diagnosis of the patient was compound heterozygous CPS1D. CONCLUSION: This study described the specific clinical characteristics and the variations of physiological and biochemical indices in a Chinese neonatal patient with CPS1D, which facilitated the diagnosis and mechanism research of the disease. Two novel causative missense mutations were identified, which enriched the mutation spectrum of CPS1D in China and worldwide. Advice of prenatal diagnosis was given to the family for a new pregnancy.

[Novel therapies in neurometabolic diseases: the importance of early intervention]. / Terapias novedosas en enfermedades neurometabolicas: importancia de una intervencion precoz.

INTRODUCTION: Individually, neurometabolic diseases are ultra rare, but for some of them there is an effective treatment. DEVELOPMENT: Several recent therapeutic advances are reviewed. Today, the possibilities of treatment for lysosomal diseases have improved. In recent years the use of enzyme replacement therapy has become more widely extended to treat mucopolysaccharidosis type IVA (Morquio A), mucopolysaccharidosis type VII (Sly syndrome), lysosomal acid lipase deficiency and alpha-mannosidosis. It has been proven that very early treatment of mucopolysaccharidoses can change their natural course. Intrathecal enzyme replacement therapy is being tried in some mucopolysaccharidoses with cognitive involvement, in an attempt to halt neurodegeneration. Very positive results have been obtained with genetically modified autotransplants in late-onset infantile metachromatic leukodystrophy and research is being conducted on other pathologies (mucopolysaccharidosis type III, X-linked adrenoleukodystrophy). Novel outcomes are also being achieved in the treatment of some encephalopathies that are sensitive to vitamins or cofactors: triple therapy in pyridoxine dependency, treatment with thiamine for some subacute encephalopathies with involvement of the basal ganglia, treatment with folinic acid for children with cerebral folate deficiency, or treatment with cyclic pyranopterin monophosphate in molybdenum cofactor deficiency type A. CONCLUSIONS: As neuropaediatricians we must update our knowledge, especially in the case of treatable neurometabolic pathologies, since early treatment can change their prognosis significantly.

TITLE: Terapias novedosas en enfermedades neurometabolicas: importancia de una intervencion precoz.Introduccion. Las enfermedades neurometabolicas son individualmente ultrarraras, pero algunas de ellas tienen un tratamiento eficaz. Desarrollo. Se revisan algunas novedades terapeuticas. Las enfermedades lisosomales tienen actualmente mejores posibilidades de tratamiento. En los ultimos años se ha extendido el uso de la terapia enzimatica sustitutiva a la mucopolisacaridosis tipo IVA (Morquio A), a la mucopolisacaridosis tipo VII (enfermedad de Sly), al deficit de lipasa acida lisosomal y a la alfa-manosidosis. Se ha constatado que un tratamiento muy precoz de las mucopolisacaridosis puede cambiar su historia natural. Se esta probando la terapia enzimatica sustitutiva intratecal en algunas mucopolisacaridosis con afectacion cognitiva, en el intento de frenar la neurodegeneracion. Se han obtenido resultados muy positivos con autotrasplante modificado geneticamente en leucodistrofia metacromatica infantil tardia y se esta trabajando en otras patologias (mucopolisacaridosis tipo III, adrenoleucodistrofia ligada a X). Tambien hay novedades en la terapia de algunas encefalopatias sensibles a vitaminas o cofactores: la triple terapia en la dependencia de piridoxina, el tratamiento con tiamina de algunas encefalopatias subagudas con afectacion de ganglios basales, el tratamiento con acido folinico de niños con deficiencia de folato cerebral, o el tratamiento con monofosfato de piranopterina ciclico en los defectos de cofactor de molibdeno de tipo A. Conclusiones. Los neuropediatras debemos actualizar nuestro conocimiento especialmente en aquellas patologias neurometabolicas tratables, dado que una terapia precoz puede cambiar de forma significativa su pronostico.

A saposin deficiency model in Drosophila: Lysosomal storage, progressive neurodegeneration and sensory physiological decline.

Saposin deficiency is a childhood neurodegenerative lysosomal storage disorder (LSD) that can cause premature death within three months of life. Saposins are activator proteins that promote the function of lysosomal hydrolases that mediate the degradation of sphingolipids. There are four saposin proteins in humans, which are encoded by the prosaposin gene. Mutations causing an absence or impaired function of individual saposins or the whole prosaposin gene lead to distinct LSDs due to the storage of different classes of sphingolipids. The pathological events leading to neuronal dysfunction induced by lysosomal storage of sphingolipids are as yet poorly defined. We have generated and characterised a Drosophila model of saposin deficiency that shows striking similarities to the human diseases. Drosophila saposin-related (dSap-r) mutants show a reduced longevity, progressive neurodegeneration, lysosomal storage, dramatic swelling of neuronal soma, perturbations in sphingolipid catabolism, and sensory physiological deterioration. Our data suggests a genetic interaction with a calcium exchanger (Calx) pointing to a possible calcium homeostasis deficit in dSap-r mutants. Together these findings support the use of dSap-r mutants in advancing our understanding of the cellular pathology implicated in saposin deficiency and related LSDs.

Endo-lysosomal and autophagic dysfunction: a driving factor in Alzheimer's disease?

Alzheimer's disease (AD) is the most common cause of dementia, and its prevalence will increase significantly in the coming decades. Although important progress has been made, fundamental pathogenic mechanisms as well as most hereditary contributions to the sporadic form of the disease remain unknown. In this review, we examine the now substantial links between AD pathogenesis and lysosomal biology. The lysosome hydrolyses and processes cargo delivered by multiple pathways, including endocytosis and autophagy. The endo-lysosomal and autophagic networks are central to clearance of cellular macromolecules, which is important given there is a deficit in clearance of amyloid-ß in AD. Numerous studies show prominent lysosomal dysfunction in AD, including perturbed trafficking of lysosomal enzymes and accumulation of the same substrates that accumulate in lysosomal storage disorders. Examination of the brain in lysosomal storage disorders shows the accumulation of amyloid precursor protein metabolites, which further links lysosomal dysfunction with AD. This and other evidence leads us to hypothesise that genetic variation in lysosomal genes modifies the disease course of sporadic AD.

Congenital disorders of autophagy: an emerging novel class of inborn errors of neuro-metabolism.

Single gene disorders of the autophagy pathway are an emerging, novel and diverse group of multisystem diseases in children. Clinically, these disorders prominently affect the central nervous system at various stages of development, leading to brain malformations, developmental delay, intellectual disability, epilepsy, movement disorders, and neurodegeneration, among others. Frequent early and severe involvement of the central nervous system puts the paediatric neurologist, neurogeneticist, and neurometabolic specialist at the forefront of recognizing and treating these rare conditions. On a molecular level, mutations in key autophagy genes map to different stages of this highly conserved pathway and thus lead to impairment in isolation membrane (or phagophore) and autophagosome formation, maturation, or autophagosome-lysosome fusion. Here we discuss 'congenital disorders of autophagy' as an emerging subclass of inborn errors of metabolism by using the examples of six recently identified monogenic diseases: EPG5-related Vici syndrome, beta-propeller protein-associated neurodegeneration due to mutations in WDR45, SNX14-associated autosomal-recessive cerebellar ataxia and intellectual disability syndrome, and three forms of hereditary spastic paraplegia, SPG11, SPG15 and SPG49 caused by SPG11, ZFYVE26 and TECPR2 mutations, respectively. We also highlight associations between defective autophagy and other inborn errors of metabolism such as lysosomal storage diseases and neurodevelopmental diseases associated with the mTOR pathway, which may be included in the wider spectrum of autophagy-related diseases from a pathobiological point of view. By exploring these emerging themes in disease pathogenesis and underlying pathophysiological mechanisms, we discuss how congenital disorders of autophagy inform our understanding of the importance of this fascinating cellular pathway for central nervous system biology and disease. Finally, we review the concept of modulating autophagy as a therapeutic target and argue that congenital disorders of autophagy provide a unique genetic perspective on the possibilities and challenges of pathway-specific drug development.

Diminished MTORC1-Dependent JNK Activation Underlies the Neurodevelopmental Defects Associated with Lysosomal Dysfunction.

Here, we evaluate the mechanisms underlying the neurodevelopmental deficits in Drosophila and mouse models of lysosomal storage diseases (LSDs). We find that lysosomes promote the growth of neuromuscular junctions (NMJs) via Rag GTPases and mechanistic target of rapamycin complex 1 (MTORC1). However, rather than employing S6K/4E-BP1, MTORC1 stimulates NMJ growth via JNK, a determinant of axonal growth in Drosophila and mammals. This role of lysosomal function in regulating JNK phosphorylation is conserved in mammals. Despite requiring the amino-acid-responsive kinase MTORC1, NMJ development is insensitive to dietary protein. We attribute this paradox to anaplastic lymphoma kinase (ALK), which restricts neuronal amino acid uptake, and the administration of an ALK inhibitor couples NMJ development to dietary protein. Our findings provide an explanation for the neurodevelopmental deficits in LSDs and suggest an actionable target for treatment.

Neuronopathic lysosomal storage disorders: Approaches to treat the central nervous system.

Pharmacological research has always focused on developing new therapeutic strategies capable of modifying a disease's natural history and improving patients' quality of life. Despite recent advances within the fields of medicine and biology, some diseases still represent a major challenge for successful therapy. Neuronopathic lysosomal storage disorders, in particular, have high rates of morbidity and mortality and a devastating socio-economic effect. Many of the available therapies, such as enzyme replacement therapy, can reverse the natural history of the disease in peripheral organs but, unfortunately, are still unable to reach the central nervous system effectively because they cannot cross the blood-brain barrier that surrounds and protects the brain. Moreover, many lysosomal storage disorders are characterized by a number of blood-brain barrier dysfunctions, which may further contribute to disease neuropathology and accelerate neuronal cell death. These issues, and their context in the development of new therapeutic strategies, will be discussed in detail in this chapter.

Gaucher disease: a lysosomal neurodegenerative disorder.

Gaucher disease is a multisystemic disorder that affects men and woman in equal numbers and occurs in all ethnic groups at any age with racial variations and an estimated worldwide incidence of 1/75,000. It is caused by a genetic deficient activity of the lysosomal enzyme glucocerebrosidase due to mutations in the ß-glucocerebrosidase gene, and resulting in lack of glucocerebroside degradation. The subsequent accumulation of glucocerebroside in lysosomes of tissue macrophages primarily in the liver, bone marrow and spleen, causes damage in haematological, skeletal and nervous systems. The clinical manifestations show a high degree of variability with symptoms that varies according to organs involved. In many cases, these disorders do not correlate with mutations in the ß-glucocerebrosidase gene. Although several mutations have been identified as responsible for the deficient activity of glucocerebrosidase, mechanisms by which this enzymatic defect leads to Gaucher disease remain poorly understood. Recent reports indicate the implication of complex mechanisms, including enzyme deficiency, substrate accumulation, unfolded protein response, and macrophage activation. Further elucidating these mechanisms will advance understanding of Gaucher disease and related disorders.

A diagnostic approach for cerebral palsy in the genomic era.

An ongoing challenge in children presenting with motor delay/impairment early in life is to identify neurogenetic disorders with a clinical phenotype, which can be misdiagnosed as cerebral palsy (CP). To help distinguish patients in these two groups, conventional magnetic resonance imaging of the brain has been of great benefit in "unmasking" many of these genetic etiologies and has provided important clues to differential diagnosis in others. Recent advances in molecular genetics such as chromosomal microarray and next-generation sequencing have further revolutionized the understanding of etiology by more precisely classifying these disorders with a molecular cause. In this paper, we present a review of neurogenetic disorders masquerading as cerebral palsy evaluated at one institution. We have included representative case examples children presenting with dyskinetic, spastic, and ataxic phenotypes, with the intent to highlight the time-honored approach of using clinical tools of history and examination to focus the subsequent etiologic search with advanced neuroimaging modalities and molecular genetic tools. A precise diagnosis of these masqueraders and their differentiation from CP is important in terms of therapy, prognosis, and family counseling. In summary, this review serves as a continued call to remain vigilant for current and other to-be-discovered neurogenetic masqueraders of cerebral palsy, thereby optimizing care for patients and their families.

Proteostasis: bad news and good news from the endoplasmic reticulum.

The endoplasmic reticulum (ER) is an intracellular compartment dedicated to the synthesis and maturation of secretory and membrane proteins, totalling about 30% of the total eukaryotic cells proteome. The capacity to produce correctly folded polypeptides and to transport them to their correct intra- or extracellular destinations relies on proteostasis networks that regulate and balance the activity of protein folding, quality control, transport and degradation machineries. Nutrient and environmental changes, pathogen infection aging and, more relevant for the topics discussed in this review, mutations that impair attainment of the correct 3D structure of nascent polypeptide chains may compromise the activity of the proteostasis networks with devastating consequences on cells, organs and organisms' homeostasis. Here we present a review of mechanisms regulating folding and quality control of proteins expressed in the ER, and we describe the protein degradation and the ER stress pathways activated by the expression of misfolded proteins in the ER lumen. Finally, we highlight select examples of proteopathies (also known as conformational disorders or protein misfolding diseases) caused by protein misfolding in the ER and/or affecting cellular proteostasis and therapeutic interventions that might alleviate or cure the disease symptoms.

Factors and processes modulating phenotypes in neuronopathic lysosomal storage diseases.

Lysosomal storage diseases are inherited metabolic disorders caused by genetic defects causing deficiency of various lysosomal proteins, and resultant accumulation of non-degraded compounds. They are multisystemic diseases, and in most of them (>70%) severe brain dysfunctions are evident. However, expression of various phenotypes in particular diseases is extremely variable, from non-neuronopathic to severely neurodegenerative in the deficiency of the same enzyme. Although all lysosomal storage diseases are monogenic, clear genotype-phenotype correlations occur only in some cases. In this article, we present an overview on various factors and processes, both general and specific for certain disorders, that can significantly modulate expression of phenotypes in these diseases. On the basis of recent reports describing studies on both animal models and clinical data, we propose a hypothesis that efficiency of production of compounds that cannot be degraded due to enzyme deficiency might be especially important in modulation of phenotypes of patients suffering from lysosomal storage diseases.

Neuronopathic lysosomal storage diseases: clinical and pathologic findings.

BACKGROUND: The lysosomal-autophagocytic system diseases (LASDs) affect multiple body systems including the central nervous system (CNS). The progressive CNS pathology has its onset at different ages, leading to neurodegeneration and early death. METHODS: Literature review provided insight into the current clinical neurological findings, phenotypic spectrum, and pathogenic mechanisms of LASDs with primary neurological involvement. CONCLUSIONS: CNS signs and symptoms are variable and related to the disease-specific underlying pathogenesis. LAS dysfunction leads to diverse global cellular consequences in the CNS ranging from specific axonal and dendritic abnormalities to neuronal death. Pathogenic mechanisms for disease progression vary from impaired autophagy, massive storage, regional involvement, to end-stage inflammation. Some of these features are also found in adult neurodegenerative disorders, for example, Parkinson's and Alzheimer's diseases. Lack of effective therapies is a significant unmet medical need.